Blank shaping fixture



July 4, 1944. c. E. ARCHER BLANK SHAPING FIXTURE Filed Oct. 15, 1942 2 Sheets-Sheet 1 3 a Z W m n r 1A ZN E W S 5 W M 7 C 0% a 23 n? I. g it \.L T. w ww July 4, 1944. Q ARCHER 2,352,608

BLANK SHAPING FIXTURE Filed Oct. 15, 1942 2 Sheets-Sheet 2 V fiwerzor' Chgf les E'Aro/Zer Patented July 4, 1944 BLANK SHAPING FIXTURE Charles E. Archer, Birmingham, Mich., assignor to Ex-Cell-O Corporation, Detroit, Mich, a corporation of Michigan Application October 15, 1942, Serial No. 462,128

16 Claims.

My invention relates to a blank shaping fixture and more particularly to a fixture for developing master cams which are employed to control certain relative movements of aturning tool or agrinding wheel and a rotating piston in the precision production of pistons for internal combustion engines.

In high specific output engines, such as those for airplanes, the piston, which is of the solid skirt type as distinguished from a split skirt type, fits the cylinder more loosely when cold than at normal operating temperature, and it is necessary in shaping the piston to allow for this expanding action to avoid undue friction and excessive wear of the piston and cylinder wall. It is desired that the piston be truly cylindrical at the operating temperature, but it has been ascertained that due to its relative remoteness from the coolant or the air cooling fins and the diflerences in rigidity of the head and skirt ends, the piston is subject to substantial changes in shape over the range from atmospheric to operating temperature. In other words, a piston which is cylindrical at operating temperature has a shape other than cylindrical at atmospheric temperature and this shape will generally vary from end to end of the piston. I The development of master cams for determining the cold shape of this piston has been a serious problem.

The required shape of the piston can only be determined empirically and it has been found that, in general, the shape of the ring groove end at atmospheric temperature will differ from the shape of the skirt end. Neither end is truly circular and their respective peripheries are composed of a plurality of circular arcs, some of which are struck from centers eccentric to the geometric axis of the piston. Because the piston is straight-sided, it is important that the longitudinal elements composing the lateral surface of the piston shall be straight lines extending between the ends of the piston. These elements are defined by the intersection with the piston only necessary, therefore. to make a former cam are eflectuated will be ring for each piston and whoseprofile may bela dimensional duplicate, or larger or smalierfthan the corresponding'piston end accordingto some ratio, and to freely surround and bridge between these rings a beam-like element which also has. a straight line characteristic, such as a cylindrical sleeve having concentric inner and outer surfaces. i

When the rings are mounted for simultaneous rotation around a common axis and are related to each other in the same manner asthe corresponding piston ends, it will be obvious'that transverse shifts of the sleeve by the cam rings rotating within the sleeve can be translated into a movement of a master cam blank towards. and away from a grinding .wheel or turnin $6 1, {or example, or of the wheel or tool relative to the blank. Movement of that portion oi the :sleeve opposite either cam rin wil controlled Y that ring and will accordingly resultin a similar shaping of the corresponding end-otthe' blank, while movementsot intermediate portions of the sleeve will hev efi'ectedby'the conjoint action of therings.

A iurther object is to. provide a fixture incorporating the above former cam, which is capable of being mounted on the shii'table-talol'e ota standard grinding machine and is adapted to either i'orm master cam blanks (orsubsequent use in other turning or grinding machines, orto directly process pistons.

These and further objects 0! my invention will be set forth in the following specification, reference being had to the accompanying drawings, and the novel means by which said objects definitely pointedv outin the claims. 1 I

Inthe drawings:

Figure 1 is a side elevation of my improved fixture, partly in section, showing the same in working relation to a grinding machine.

Fig. 2 is a section along the line 2-4 in Fig. l.

Fig. 3 is an end view of the fixture looking in the direction of the arrow 3 ln-Pl8.- 1.

Figs. 4 and 5 are elevations oftwo of the former cam rings utilized in my fixture.

Fig. 6 is an edgewiseview oi either of the rings shown in Figs. 4 and 5, but for purpose of description will be regarded as a view of the ring shown in Fig. 4.

By way of example, my inproved fixture is shown in connection with astandard metal vremachine. The table is given a reciprocating or traversing movement relative to a cutting tool I: which is secured to a spindle I2 that is driven by a pulley |4 forming part of the machine. The

cutting tool may be of anysuitable character, and in the present instance is shown as a grinding wheel, the flxture forming part of a grinding machine.

A cradle I2 is rockably mounted on a pair of bearings l2 secured to the bed plate I2, and is urged in a clockwise direction as viewed in Fig. 3, i. e., toward the grinding wheel l2, by means of springs I 1 whose lower ends rest on the bed plate i2 while the upper ends extend within pockets |2 forming part of the cradle i2.

The cradle I2 is provided with a tailstock l2 and a headstock 20 which are spaced from each other as illustrated in Figs. 1 and 2 to receive therebetween a former cam and the work to be shaped as hereinafter described. A tail center 2| is mounted in a plunger 22 that is reciprocable within the tailstock l2, but is held against rotation relative thereto and is normally urged toward the left, as viewed in Fig. 2. by a helical spring 22 adjustably loaded by a bushing 24 threaded interiorly of the tailstock. A stem 22 has one end threaded in the plunger 22 and ex tends outwardly through the head of the bushing 24 for pivotal connection by means of a pin 22 with a release handle 21. When the tail center 2| is in the work engaging position illustrated in Fig. 2, the handle 21 is held in position by means of a spring actuated detent pin 22 that seats in a recess 22 provided in a head 22 forming part of the stem 22. The handle 21 is also provided with a cam surface 2| which, when the handle 21 is rocked downwardly from the position shown in Fig. 2, bears against the end surface of the bushing 24, and thereby withdraws the plunger 22 and the associated tail center 2| toward the right, or in a releasing direction.

The tapered end of a spindle 22 is journaled in bearings 22 in the headstock 22 and extends leftward beyond the latter for connection by means of a universal coupling "to a driving head 24 forming part of the grinding machine, thus permitting rocking movement of the cradle l2. The right end of the spindle 22 carries a live center 22 between which and the tail center 2| is supported an arbor 21 comprising an integrally formed flange 22 and cylindrical body 22 and a disk 42. A cam blank 4| is slipped over the body 39 and is clamped between the flange 22 and disk 42 by a nut 42 that is threaded on the right end of the arbor 21.

That portion of the spindle 22 which extends to the right of the headstock 22 is cylindrical, as indicated by the numeral 42, and at the Junetion of the spindle portions 22 and 42 is formed a flange 44. Between the flange 44 and the right end of the spindle portion 42 is mounted a former cam assembly which constitutes one of the features of my invention. In succession and beginning at the flange 44, this cam assembly comprises a disk 42, a cam ring 42, a spacerspool 41 keyed to the portion 42, a cam ring 42, a disk 42 and a nut 22 which is threaded on the right end of the portion 42 and serves to clamp the indicated parts of the cam assembly against the flange 44. The cam ring 42 carries a pin 2| which is received within a slot 22 provided in the adjacent end 01 the spool 41, while the cam ring 42 carries a pin 22 whose opposite ends are respectively received in a solt 24 provided in an adjacent end of the spood 41 and a slot 22 in the disk 42. The pins 2| and 22 accordingly register the cam rings with respect to the spool 41 and hence with respect to each other. Driving meral 22 in Fig. 6 to provide a land 22 centrally faces.

disposed between the opposite faces or flanks of the ring. A similar land 22 is likewise formed around the cam ring 42 and freely surrounding and bridged between these lands in a cylindrical sleeve 2| having concentric inner and outer sur- Endwise movement of the sleeve 2| relative to the cam rings is prevented by the disks 42 and 42 which are appropriately shouldered for this purpose,,but the ends of the sleeve 2| are not gripped byfthe disks 42 and 42.

The cam ring 42 is intended to serve as a guide for shaping the left end of the blank 4|, while the ring 42 serves a similar purpose in eonnec-- tion with the right end thereof. When used to process axpiston having the characteristics above would control the shaping of the piston at the ring groove end.

The ring 42 is provided with a circular axial opening 22 having a diameter sufllcient to provide a snug flt on the spindle portion 42. For reasons noted, the periphery of the land 22 is not circular, but is composed of a plurality of arcs which are struck from centers that are determined empirically. Since the curvature of onehalf of the land 22 is identical with the other hair it will be convenient to consider this shaping with respect to that portion of the ring 42 which is disposed below the horizontal diameter 22 in Fig. 4. Moving clockwise around the ring beginning at the right end of the diameter 22, the land 22 is successively composed of arcs struck from the geometric center 24 of the ring, a center 22 above the diameter 22 and to the left of a diameter 22 normal thereto, a center 21 above the diameter 22 and on the diameter 22, a center 22 located above the diameter 22 and to the right of the diameter 22, and finally an arc struck from the geometric center 24. The foregoing centers are appropriately duplicated and correspondingly arranged for the arcs of the land 22 in the upper half of the ring 42. The ring also includes an aperture 12 in which is mounted the registering pin 2| to which reference has already been made.

The peripheral shape of the land 22 for the ring 42 is somewhat simpler for the condition specified, since it is intended to form that end of the blank 4| which will shape the head end of the piston. Due to its more rigid construction, the head end is less subject to deformation over the temperature range from atmospheric to operating. As before, the land shape is duplicated on opposite sides of any given diameter of the ring and, considering the horizontal diameter 1| in Fig. 51 as a starting point and directing attention to the lower half of the ring, moving clockwise from the right end of the diameter 1|, the land is composed of arcs successively struck from the geometric center 12 of the ring, a center 12 disposed above the diameter 1| and on the includes an aperture 18 which receives the registering pin 53.

It willbe understood that the centers for the several arcs above described for both cam rings may vary for different designs of pistons or for any type of master cam Or other blank or part which it is desired to form. A

A disk 11 rides on the outer surface of the sleeve 6| and is secured to a shaft 18 that is supported for rotary and endwise movement in and relative to bearings 19 and 80 carried by the bed plate Ill. The disk 11 is held against endwise movement by means of a pair of balls 8| which straddle and bear on the opposite face of the disk 11 and are carried in an arm 82 that is sup ported by a fixed part 83 of the grinding machine.

From the foregoing, it will be understood that as the spindle 32 rotates, the table II is given a motion of reciprocation and traverse relative to the grinding wheel l2 so that cam blank 4| and sleeve 8| similarly move with respect to the wheel l2 and the disk 11 and the springs I'I constantly bear the blank 4| against the wheel I! and the sleeve 8| against the disk ll. If it be considered that the fixture is employed to shape the cam blank 4| for the subsequent processing of pistons of the character described and that the cam rings 48 and 48 have peripheral shapes corresponding to the portions of the piston lateral surface adjacent the skirt and head ends, respectively, it will be obvious that when the disk I1 is opposite the ring 46, the left end of the cam blank 4| will have imparted thereto a shape similar to the shape of the cam ring 48 and when the disk 11 is opposite the cam ring 48, the right end of the blank 4| will be shaped similar to the last mentioned cam ring. During this operation, the free relation between the sleeve GI and rings 46 and 48 is effective, in conjunction with the springs ll, to rock the cradle l5, thereby varying the distance between the axes of the wheel I! and the blank 4|. The sleeve 8| is internally cylindrical and, therefore, cannot have full peripheral contact with either of the cams. Due

to the. biasing force of the springs H, the cam follower 11 will cause the inside longitudinal straight line element of the sleeve 8| to contact the peripheries of the cams 48 and 48 in the axial plane of rotation as shown by Fig. 2. There is a relative floating movement or adaptation of the sleeve transaxially in each increment of rotation of the cams 48 and 48 as determined by the shapes of the cams, and the conjoint action thereof serves to define a straight line element in any angular position of rotation defining the form at all longitudinal points between the cams. Accordingly, the shaping of the blank 4| is accomplished by a combination of two movements: one longitudinally of the blank axis and across the peripheral surface of the grinding wheel, and the other transversely of the blank axis.

An important feature of the invention resides in the recognition that since it is desired that that piston be straight-sided, the end shapesof the piston constitute limiting factors, regardless 01' their particular forms and whether or not 78 symmetrically related, and intermediate shapes can be precisely obtained by means of the straight-sided sleeve 8|. In other words,- when the disk l'l rides any portion of the sleeve 8! between the rings 48 and 48, the shape which is thereby given to the corresponding portion of the cam blank 4| is a function of the conioint action of the rings 48 and 48.

It will be further understood that while my improved fixture is more directly intended for the production of cam blanks that are subsequently used in other machines for the final processing of pistons, such pistons may be shaped directly in my fixture by substituting the same for the cam blank 4|.

I claim as my invention:

1. A blank shaping fixture for mounting on a machine having a material removing tool comprising a carrier, the tool and carrier being arranged for relative traverse and movements toward and from each other, means on the carrier for rotatably supporting a blank for shaping in contact with the tool, and a rotary former cam for controlling said to and fro movement during said relative traverse comprising a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank and a sleeve freely encircling and bridged between the rings.

. 2. A blank shaping fixture for mounting on a machine having a material removing tool comprising a carrier, the tool and carrier being arranged for relative traverse and movements toward and from each other, means on the carrier for rotatably supporting a blank for shaping in contact with the tool, and a rotary former cam for controlling said to and fro movement during said relative traverse comprising a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank and a cylindrical sleeve having concentric inner and outer surfaces freely encircling and bridged between the rings.

3. A blank shaping fixture for mounting on a machine having a material removing tool comprising a carrier, the tool and carrier being arranged for relative traverse, means on the carrier for rotatably supporting a blank for shaping in contact with the tool, a rotary former cam on the carrier comprising a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank, a sleeve freely encircling andbridged between the rings, and a part cooperating with the sleeve for effecting a relative to and fro movement of the carrier and tool during traverse.

4. Ablank shaping fixture for mounting on a machine having a material removing tool comprising a carrier, the tool and carrier being arranged for relative traverse, means on the carrier for rotatably supporting a blank for shaping in contact with the tool, a rotary former cam comprising a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank, a cylindrical sleeve having concentric inner and outer surfaces freely encircling and bridged betwen the rings, and a part cooperating with the sleeve for effecting a relative to and fro movement of the carrier and tool during traverse.

5. A blank shaping fixture for mounting on a machine having a material removing tool comprising a bed traversable relative to the tool, a carrier rockable on the bed, means on the car.- rier for rotatably supporting a blank for shaping, spring means active against the carrier for resiliently holding the blank in contact with the tool, a rotary former cam on the carrier comprising a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank, a sleeve freely encircling and bridged ,between the rings, and a part cooperating with the sleeve and held against traversing movement relative to the tool for effecting a to and fro movement of the carrier relative to the tool.

6. Ablank shaping fixture for mounting on a machine having a material removing tool comassaeoa to be shaped, comprising a pair of spaced cam rings having peripheral shapes similar to the prising a bed traversable relative to the tool, a

carrier rockable on the bed, means on the carrier for rotatably supporting a blank for shaping, spring means active against the carrier for resiliently holding the blank in contact with the tool, a"rotary former cam on the carrier comprising a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank, a cylindrical sleeve having concentric inner and outer surfaces and freely encircling and bridged between the rings, and a part cooperating with the sleeve and held against traversing movement relative to the tool for effecting a to and fro movement of the carrier relative to the tool.

7. A blank shaping fixture for mounting on a machine having a material removing tool comprising a bed traversable relative to the tool, a carrier rockable on the bed and biased toward the tool, means on the carrier for rotatably supporting a blank for shaping in contact with the tool, a rotary former cam on the carrier comprising a pair of spaced cam rings having peripheral shapes s milar to the final shaping of the respective ends of the blank, a sleeve freely encircling and bridged between the rings, and a rotatable disk riding on the periphery of the sleeve and held against traverse relative to the tool for effecting a to and fro movement of the carrier relative to the tool.

8. In mechanism for shaping the peripheral surface of a blank, the combination of a material removing tool, a carrier, means on the carrier for rotatably supporting a blank for shaping in contact with the tool, means for relatively traversing the tool and carrier, a rotary former cam on the carrier compris ng a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank, a sleeve freely encircling and bridged between the rings, and a part cooperating with the sleeve and held against traverse relative to the tool for effecting a to and fro movement of the, carrier relative to the tool.

9. In. mechanism for shaping the peripheral surface of a blank, the combination of a mate-v rial removing tool, a carrier, means on the carrier for rotatably supporting a blank for shaping in contact with the tool, means for relatively traversing the tool and carrier, a rotary former cam on the carrier comprising a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank, a cylindrical sleeve having concentric inner and outer surfaces freely encircling and bridged between the rings, and a part cooperating with the sleeve and held against traverse relative to the tool for effecting a to and fro movement of the carrier relative to the tool.

10. Former cam means for controlling the relative to and fro movement of a material removin: tool and a blank whose peripheral surface is final shaping of the respective ends of the blank, and a radially floating sleeve freely encircling and bridged between the rings for engagement with a part traversable relative to the sleeve.

11. Former cam means for controlling the relative to and fro movements of a material removing tool and a blank whose peripheral surface is to be shaped, comprising a pair of spaced cam rings having peripheral shapes similar to the final shaping of the respective ends of the blank, and a cylindrical sleeve having concentric inner and outer surfaces freely encircling and bridged between the rings for engagement with a part traversable relative to the sleeve.

12. A blank shaping fixture for mounting on a machine having a material removing tool comprising a bed traversable relative to the tool axially of the blank, a carrier on said bed movable transversely toward and from the tool and being biased in one direction, means on said carrier for rotatably supporting a blank for shaping in contact with the tool, a former cam rotatable 5 on the carrier in timed relation with the blank and comprising a pair of axially spaced rotary cams having different peripheral shapes corresponding to the form to be produced respectively on the opposite ends of the blank, a cylindrical sleeve encircling said cams and adapted for internal contact therewith, a cam follower held against traverse relative to the tool and engaging the outer periphery of said sleeve to determine the position of said carrier in opposition to the biasing force, said sleeve being confined against longitudinal movement relative to said cams and being traversable with the blank relative to said follower in a direction axially of. the blank, whereby said follower will cause successive longitudinal straight line elements of said sleeve to contact and bridge said cams so as to define the form throughout the length of the blank as determined by the respective shapes of said cams.

13. A blank shaping fixture for mounting on a machine having a material removing tool comprising a bed traversable relative to the tool axially of the tool, a carrier on said bed movable transversely toward and from the tool and being biased in one direction, means on said carrier for rotatably supporting a blank for shaping in contact with the tool, a former cam rotatable on the carrier in timed relation with the blank and comprising a pair of axially spaced rotary cams independently rotatably adjustable to vary their relative angular phase and having unlike peripheral shapes corresponding to the form to be produced respectively on the opposite ends of the blank, a sleeve of transversely symmetrical form encircling said cams and adapted for internal contact therewith along longitudinal straight line elements, a cam follower held against traverse relative to the tool and engaging the outer periphery of said sleeve to determine the position of said carrier in opposition to the biasing force, said sleeve and cams being traversable with the blank relative to said follower in a direction axially of the blank, whereby said follower will cause successive longitudinal straight line elements of said sleeve to contact and bridge said cams so as to define the form throughout the length of the blank as determined by the respective shapes of said cams.

14. A blank shaping fixture for mounting ona machine having a material removing tool com.-

carrier on said bed movable transversely toward and from the tool and being biased in one direction, means including a drive shaft on said carried for rotatabLy supporting a blank for shaping in contact with the tool, a rotatable former cam on said shaft comprising a pair of axially spaced rotary cams having V-shaped peripheral faces corresponding to the form to be produced respectively on the opposite ends of the blank, a sleeve loosely encircling said cams and adapted for interndl contact with said faces, a rotary cam follower held against traverse relative to the tool and peripherally engaging the outer periphery of said sleeve to determine the position of said carrier in opposition to the biasing force, said sleeve being tTaversable with the blank relative to said follower in a direction axially of the blank, whereby said follower will cause successive longitudinal elements of said sleeve upon engagement by said follower to contact and bridge said cams so as to define the form throughout the length of the blank as determined by the respective shapes of said cams.

15. A blank shaping fixture for mounting on a machine having a material removing tool comprising a bed traversable relative to the tool, a carrier mounted on said bed movable transversely toward and from the tool and being biased in one direction, means on said carrier for rotatably supporting a blank for shaping in contact with the tool, a rotatable former cam mounted on said carrier for transverse movement thereby with the 'blank, means for rotating the blank and said former cam in positive timed relation, said former cam comprising a pair of axially spaced rotary cams having peripheral faces contoured to correspond to the form to be produced respectively on the opposite ends of the blank, a longitudinal bridge member contacting at opposite ends against the faces of said rotary cams at one side in a predetermined axial plane of said former cam, and being subject to angular variation relative to the axis of said former cam in accordance with the relative radial dimensions of said rotary cams in each increment of rotation of the latter through said plane to determine the form to be produced on the blank at successive points intermediate the opposite ends, and a cam follower held against traverse relative to the tool and arranged to travel along said bridge member in contact therewith in opposition to the biasing force to determine the transverse position of said carrier in the rotation of said former cam throughout the traverse of said bed relative to the tool.

16. A blank turning device comprising, in combination, a rotary former cam, a cam follower coacting with said former cam, means for eflecting relative traverse between said cam and said cam follower axially of said cam, means for effecting relative movement between said cam and said cam follower transversely of the axis of said cam in accordance with the contour of said cam, a cutting tool, a support for a rotary blank to be turned, means for rotating said cam and said support in timed relation, means for efiecting relative traverse through cutting engagement between said tool and the blank axially of the blank and in timed relation to the traverse between said cam and said cam follower, and means responsive to the relative transverse movement between said cam follower and the axis of said cam for relatively positioning said tool and the blank in timed relation transversely of the axis of the blank, said cam comprising a pair of relatively fixed and axially spaced rotary cam disks having peripheral faces contoured to correspond to the form to be produced respectively on the opposite ends of the blank, and a longitudinal bridge member operatively contacted on one side by said cam follower and operatively contacting on the other side and at opposite ends against the faces of said cam disks in a predetermined axial plane of said cam, said bridge member being supported for angular adaptation relative to the axis of said cam in accordance with the relative radial dimensions of said cam disks in each increment of rotation of the latter through said plane.

CHARLES E. ARCHER. 

